Blown arc lamp



E. GRETENER BLOWN ARC LAMP Dec. 22, 1953 Filed Jan. 15, 1951 INVENTOR: cigmmw ATTORNEYS.

Patented Dec. 22, 1953 UNITED STATES PATENT OFFICE BLOWN ARC LAMP Edgar Gretener, Zurich, Switzerland Application January 15, 1951, Serial No. 206,019

9 Claims. 1

The present invention is relative to blown arc lamps, particularly to blown arc lamps for the illumination of motion picture projectors and studios.

Blown electric arcs which have now come into use to a certain extent in high-intensity are lamps, achieve increased brilliance of the are by means of air blast concentration. An air blast concentrically surrounds the arc discharge and is generally dir cted from the positive electrode towards the negative one thus confining both are discharge and tail flame to a cylindrical space in front of the positive crater. The air blast mixed with the hot gases and evaporation products of the tail flame is received on the negative side by a suction pipe the orifice of which surrounds the tip of the negative electrode. In order to lead away the entire air blast and entrained gases, a slight vacuum is kept up inside this suction pipe.

This vacuum is generally obtained by the employment of a rotating mechanical exhaust blower, which, however, implies numerous inconveniences. T .e blower rotor and its bearings are exposed to the current of hot and corroding gases whereby the wear of these parts is considerably increased, and the removal of evaporation products depositing during operation inside the blower and the associated exhaust duct is very inconvenient. In order to reduce the length of such exhaust ducts as far as possible the exhaust blower must be located within the shortest possible distance from the lamp, preferably on the lamp itself. This demands substantial reduction of the diameter of the rotating parts or" the blower in view of the restrictions prevailing as to the overall dimensions of the lamp. The necessary speed of rotation resulting from the reduced diameter of the blower wheel by far exceeds the speed of rotation of normal asynchronous motors directly branched to the A. C. mains supply. Commutator motors which must be employed instead are, however, considerably more expensive and require additional servicing, such as regular cleaning of the commutator and replacement of the carbon brushes. Furthermore the einplo'yement of a rotating blower gives rise to substantial noise which is transmitted fully to the lamp house as the blower is fixedly connected to the same. A silencer mounting of the blower on the laniphouse on the other hand is undesirable as it implies a more complicated design of the lamp.

It is therefore an object of the present invention to provide a blown arc lamp of simplified construction and with increased safety of operation. It is a particular object of the invention to provide a simple and cheap oevice for producing the exhaust vacuum required by blown arc lamps thereby reducing the requirements for attendance and service of such lamps.

It is furthermore an object or" the invention to reduce substantially the noise produced a blown arc lamp during operation thus oermitting employment of such lamps even one. 1' circumstances where noise is detrimental.

It is another object of the inve lion to permit operation of more than one blown arc lamp by a single common blower thus reducing instal tion costs noise and increasing reliability safety of operation of projector plants in motion picture theatres.

ihese and other objects of th present invention will become apparent l the following clesoription explaining in detail pr ferred embocli ments of the same with refe ence to the accompanying drawings, where Fig. 1 represents schematically and in part in a sectional view a blown arc lamp according the invention,

Fig. 2 is a fragmentary and schematic view another embodiment, and

Fig. 3 schematically illustrates the operation two blown arc lamps by a single common blower according to the invention.

In Fig. 1, which schematically shows a blown arc lamp, I represents the negative and the positive electrode, a high-intensity ca con being preferably employed as positive electi It i well known, that the core of such higli-intensitcarbons is an admixture of e-earth salts whereby the brilliancy oi r 4 is greatly enhanced. The negative carbon prefe ably passes through a hole in the center of concave refiecto 3, which in a well known manner s centrate the light lino: ema The positive carbon 2 is locat the negative carbon and s A tive head 4. Both carbons are c lel to the direction of their align to compensate for consumption. of the bons. Devices effecting ment or o matically or by hand are well k o the and are therefore orly scheniatical the drawings, via. threaded 5 Likewise all such parts of ooin I are well nown but not necessary for the following Both carbons l and 2 and th accommodated in a lamp house l. be illuminated, e. g. the aperture of accavoa of lamp house For the purpose of air blast concentration the positive head incorporates a nozzle arrangement, producing an air blast Q concentrically surrounding the arc discharge it. This air blast is received by a suction pipe is which concentrically surrounds the tip of the negative electrode l. duce air blast 9 is supplied to the positive head 4 by an air duct i5. Blown arcs of this kind are well known in the art and have been described e. g. in my pending U. S. application Serial No. 85,896, filed on April 6, 1949, now Patent No. 2,540,255, granted February 6, 1951.

The surrounding air blast 9 carries away with it evaporated and oxidized matters from the positive carbon, and must therefore be entirely removed from the lamp house through the suction pipe. Otherwise damaging and staining of the reflector may ensue and noticeable additional heating of the lamp house will be caused. A slight vacuum is therefore created in the suction pipe so that the entire air blast including the arc gases is aspirated. It may additionally be necessary to ventilate the lamp house to remove residual fumes and to cool the parts heated by radiation from the arc. A ventilation port it may be provided for this purpose at the top of the lamp house i.

It is evident that in case of the use or mechanical blowers either two separate blowers are necessary, or a double blower with two wheels, one producing the concentrating air blast and the other the vacuum in the suction pipe. Both alternatives present considerable complication of the design and cost of the lamp. These complications are increased still further when the natural thermal draft inside the lamp house is not sufiicient for ventilating the same for in that case either an additional third exhaust blower or a three wheel blower is required.

Such inconveniences are avoided by the present invention by the employment of an injector it which is fixedly mounted at the back of lamp house i and which serves to produce the necessary partial vacuum inside the suction pipe. Fresh air of suficient pressure and in sufiicient quantity is supplied to the input iii of the device. The blower supplying that air may be located separate from the lamp and is not shown in Fig. 1. The air traverses a tubular member 28 which contracts at 2! to form a nozzle and then opens out to form a conically diverging funnel 22. A second tube 23 is mounted concentrically inside said tubular member 253 and communicates with the suction pipe by an exhaust tube 33. The tube 23 is cut off square at the end and this outlet opening of this tube 23 is located adjacent to the contracted part 2! of member 2d thus 1.;- ing an annular gap between tube 23 and member 2b. This annular gap acts as injector nozzle. Due to its pressure the air supplied to member 29 will issue from the annular gap 24 with great speed and thereby produce a partial vacuum inside tube 23 to effect the withdrawal of the arc gases from the suction pipe is through the exhaust tube is.

A mixture of gases will issue from the funnel consisting of the supply air admitted at it and The air necessary to pro the vaporized and oxidated products of the blown draft inside the tubular member 25, the bottom end of which communicates with the ventilation port it of the lamp house i. This draft serves to ventilate the lamp house and at the time to remove remaining are gases and fumes still present inside the lamp. The end of tubular member 25 preferably leads to the open air. A silencer pct 26 may, however, be employed in the course of the exhaust duct. Such silencer pots are well known and will prevent noise conducted by the stream of gases to penetrate into the open air, thus considerably reducing the noise generated by the injector device.

An arrangement as just described thus represents a double action injector the two nozzle systems which are arranged in succession. The mixture or" gases issuing out of the first nozzle system acts as propelling medium for the second one. The device is highly eiiective if gases or fumes are to be aspirated from two diiierent channels. It is to be understood that the design of the two nozzle systems is not limited to the construction shown by Fig. 1. So e. g. the vacuum in tub-e 23 may be produced by a nozzle supplied with fresh air and arranged inside tube 23. Or the draft inside tubular member 25 may be generated by a nozzle, similar to the orifice of tubular member 28, outwardly surrounding said member 25.

If employed according to the present inven tion in cooperation with a blown arc lamp, the first nozzle system is supplied with fresh air of sufficient pressure and produces the partial vacuum required in the suction pipe on the negative side of the lamp. The second system produces the draft necessary to ventilate the lamp house and in its turn is fed by the mixture of supply air and arc of gases issuing from the first nozzle system.

The advantages of a double acting injector blown arcs are evident. The partial vacuum required by the negative side of the arc and the draft for lamp house ventilation are simulta neously generated. No moving or rotation parts are employed and no such parts can get into contact with the hot corroding arc gases. Life and reliability of the lamp is thereby considerably increased. The mechanical construction of the injector, consisting only of a small number of tubular parts is considerably simplified and much cheaper than a mechanical exhaust blower. Cleaning of the lamp particularly of the exhaust ducts is simplified. The absence of all moving parts implies practically suppression of any noise and the injector may be united with the lamp house to form one single unit, where no additional noise damping members are required. Only a very small part of the exhaust duct is exposed to the stream of hot corroding gases, whereas the mixture of gases issuing from the injector contains a surplus of fresh air and therefore pos sesses only a slightly elevated temperature.

In order to reduce further eventual oxidation of the exhaust tube by the hot arc gases, this tube may be cooled by the supply air. shown by Fig. 2, representing a modified part of the lamp as shown by Fig. l, where identical parts are given the same reference numerals as in Fig. 1. The rearward end ea or the first tubular duce the tendency of said tube to be oxidized by the hot arc gases.

for

This is The blower supplying fresh air to the injector need no longer be located closeto the lamp as the tube 21 conveying fresh air to the blast nozzle 4 and the exhaust apparatus may have a certain length without incurring any disadvantages. Thus favorable conditions prevail for the construction of the blower. Utmost reduction of space no longer is an essential condition. Consequently the diameter of the blower may be increased thereby reducing the necessary speed of rotation. This permits operation of the blower by a normal asynchronous motor branched to the A. C. mains supply. The supply blower may be set up apart from the lamp, thus permitting mounting on silencing members. Silencer mounting and the low speed of rotation considerably reduce the noise produced by the blower;

The residual noise still generated inside the injector is caused by the hot air flow and may be further reduced, as already mentioned, by the insertion of silencer pot 26 into the exhaust duct. Additional silencers may shut off the entire lamp house against the surrounding space or be inserted e. g. where the back part of the negative carbons issues from the suction pipe. Thereby the noise generated by the entire lamp is practically reduced to zero.

Additionally fume or dust filters of the well known kin-d may be employed to clean the issuing gas from the arc fumes. In this case exhaust gas ducts for the removal of arc fumes may even be dispensed with.

The blower nozzles on the positive head of the blown arc may be supplied by the same supply blower. Preferably the supply tube 21 is tapped by the tube before entering into the injector device.

A blown arc with double injector according to the present invention offers particular advantages for motion picture projection. In general two projectors with associate lamps are alternately employed. The injectors of both lamps may be supplied by a single supply blower which alternately supplies one of the lamps thereby considerably reducing installation costs. The continuous output of the blower motor consequently may be adapted to the supply of one lamp only. During the period of change over from one projector to the other the blower supplies air to both lamps and the efficiency and output of the injectors are reduced. Reduced output of the injectors may, however, be tolerated for a short interval due to a certain indifference of the blown arc to fluctuations of intensity of the air blast and of the draft in the suction pipe.

An arrangement of two blown arc lamps supplied by one common blower is shown in Fig. 3. Two lamps 30 and 3|, which may be constructed in the same way as the lamp shown by Fig. l, serve to illuminate the aperture of two projectors 32 and 33, one projector and one lamp each forming a single unit. The double injectors 34 and 35 provide suction and ventilation to lamps 30 and 3!, respectively. Both injectors are supplied with fresh air by the same supply blower 36. The blower 36 located separately from the lamps is mounted on silencing springs or rubber mountings 31 and is connected via a flexible tubular member 39 to the supply tubes 38 leading to lamps 30 and 3 I. The transmission of noise from the blower to the lamps is thereby effectively suppressed. As has already been mentioned the continuous output of the motor of the blower 36 is sufficient to supply air to one injector only. Two valves 40 and 41 are provided in the supply 6 tubes 38 permitting to shut oil one or the other of the injectors. Both valves will be opened during the short period of change over from one projector to the other, i. e. when both arcs are operated. During this period the air supply of each lamp drops below the normal value. Mutual interlocking devices actuating or looking valves 40 and 4| may additionally be employed to prevent both injectors from remaining connected to the blower, after the change over, so that the air is supplied only to the operated lamp alone.

Alternatively the separate blower may be designed to deliver the full amount of air required by both lamps during the interval of change over, the blower motor taking overload during. this period. In this case an additional choke may be provided in the supply line limiting the air pressure to its required value when only one lamp is operated. This choke may be governed by said interlocking device in such a way that the choke is active only when one of valves 40 or 51 is closed.

The invention off rs further considerable advantages if the blown arc lamp is to be employed for lighting of motion picture studios, where the possibility of separating supply blower and lamp offers particular advantages. The lamp may be moved about freely and need only be connected to central supply blower by a thin hose. Due to the absence of a rotating mechanical blower on the lamp practically no noise is generated which is highly advantageous when taking talking pictures.

In the foregoing specification reference has been made exclusively to the employment of a double injector in blown arc lamps which constitutes its main field of application. This, however, is by no means to be construed as limiting, and double injector of the kind described may advantageously be employed whenever the removal of gases from diiferent channels is to be effected by one single device of simple construction.

I claim:

1. In a blown arc lamp, the combination with a lamp housing, a positive carbon electrode, a hollow electrode head. surrounding said electrode and constituting a nozzle to direct a blast of air coaxial with and away from the arc end of said electrode, a negative electrode having an arcing tip in alinement with the axis of the positive electrode, and a suction pipe with an inlet opening adjacent the arc end of said negative electrode to receive said air blast and are gases entrained thereby; of means for establishing a reduced pressure within said suction pipe, said means comprising an injector into which said suction pipe opens, a blower spaced from and supported independently of said lamp housing, and a pipe connection from said blower to said injector to establish an air current through the same.

2. In a blown arc lamp, the invention as recited in claim 1, wherein said pipe connection includes a flexible section to preclude the transmission of blower noise and vibration to said lamp housing.

3. In a blown are lamp, the invention as recited in claim 1, wherein said injector comprises a tubular member having a contracted intermediate portion followed by a conically diverging portion, and said suction pipe extends into and axially along said tubular member with its outlet end terminating at substantially the contracted intermediate portion thereof.

4. In a blown arc lamp, the invention as recited to constitute a second injector, the inlet end of said second injector opening into said lamp housing to establish an air stream therethrough.

6. In a blown arc lamp, the invention as recited in claim 1, wherein said lamp housing is provided with a ventilating opening, in combination with a second injector energized by said blower for withdrawing air from said lamp housing through said ventilating opening.

'7. In a blown arc lamp, the invention as recited in claim 6, wherein said second injector is in tandem with said first injector, the mixture 01 air and are gases issuing out or" the first injec tor constituting the propellant medium for said second injector.

8. In a blown arc lamp, the invention as recited in claim 1, in combination with a silencer at the exhaust side of said injector.

9. In a blown arc lamp, the invention as recited in claim 1, in combination with a pipe connection from said hollow electrode head to said blower which energizes said injector.

EDGAR GRETENER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 475,544 Dobbie May 24, 1892 600,077 Horsley Mar. 1, 1898 1,082,113 Diden Dec. 23, 1913 1,318,701 Sperry Oct. 14, 1919 1,382,215 Mordey June 21, 1921 1,622,155 Koliolke Mar. 22, 1927 1,641,301 Sperry Sept. 6, 1927 1,654,653 Jordanoif Jan. 3, 1928 1,711,983 Bassett May 7, 1929 2,305,757 Beck Dec. 22, 1942 2,540,256 Gretener Feb. 6, 1951 

